Intermittent Hypoxia Does not Elicit Memory Impairment in Spinal Cord Injury Patients

Abstract

There is a critical need for new therapeutic strategies to restore motor function in patients with spinal cord injuries (SCIs), without unwanted effects. Intermittent hypoxia (IH) induces plasticity in spared synaptic pathways to motor neurons below the level of injury, which can be harnessed to elicit motor recovery in incomplete SCI patients.However, there is conflicting evidence regarding the effects ofIH onmemoryfunction. The aim of this studywas to assess episodic verbal and visual memory function with theComplutense verbal learning test (TAVEC)and theRey– Osterrieth Complex FigureTest (ROCF), respectively, before and after a 4-week protocol of repetitive IH combined with bodyweight-supported treadmill training (BWSTT) in incomplete ASIA C and D SCI subjects. Subjects received either IH (cycling 9%/21% FiO2 every 1.5 min, 15 cycles per day) or continued normoxia (Nx, 21% FiO2) combined with 45 min of BWSTT for 5 consecutive days, followed by 3 times per week IH and BWSTT for 3 additional weeks. ROCF Z scores between IH plus BWSTT and Nx plus BWSTT were not significantly different (p ¼ .43). Compared with baseline, IH and BWSTT group showed a significantly greater (p , .05) verbal memory performance for immediate, short-term, and long-term recall; however, it was not different from Nx plus BWSTT group in all verbal memory components (p . .05). Our results suggest that a 4-week protocol of moderate IH does not elicit visual or verbal memory impairment. Thus, repetitive IHmay be a safe therapeutic approach to incomplete spinal cord injury patients, without deleterious cognitive effects.